1. Field of the Invention
This invention relates to a radiation image read-out apparatus wherein a read out section and an erasing section are combined with each other. This invention particularly relates to a radiation image read-out apparatus which is small in size.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the amount of energy stored during exposure to the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. Nos. 4,258,264, 4,276,473, 4,315,318 and 4,387,428 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in radiation image recording and reproducing systems. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) is first exposed to radiation, which has passed through an object such as the human body, in order to store a radiation image of the object thereon, and is then scanned with stimulating rays such as a laser beam which cause it to emit light in proportion to the amount of energy stored thereon during exposure to radiation. The light emitted by the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted into an electric image signal, which is used to reproduce the radiation image of the object as a visible image on a recording material such as photographic film, a display device such as a cathode ray tube (CRT), or the like.
In the aforesaid radiation image recording and reproducing systems, the stimulable phosphor sheet is used temporarily to store a radiation image until the sheet is scanned with stimulating rays and the radiation image is read out therefrom. After the radiation image is read out from the stimulable phosphor sheet, energy remaining thereon should be erased so that the sheet may be reused.
For satisfying this requirement, it has been proposed to provide a radiation image read-out apparatus with a read-out section for reading out an image stored on a stimulable phosphor sheet, and an erasing section for erasing energy remaining on the sheet.
In the proposed radiation image read-out apparatus, a cassette housing a stimulable phosphor sheet carrying a radiation image, which was stored thereon in an external image recording apparatus, is fed to a cassette holding section, and the stimulable phosphor sheet is taken out of the cassette and sent to the read-out section, where the radiation image is read out. After the read-out of the image is finished, the stimulable phosphor sheet is sent to the erasing section, where any energy remaining on the sheet is erased. The erased stimulable phosphor sheet is then taken out of the read-out apparatus and reused for image recording. In general, a plurality of the erased, reusable stimulable phosphor sheets are stacked in a stacking tray inside of the read-out apparatus, and they are still housed in the stacking tray when they are taken out of the read-out apparatus. Since when they are to be reused for image recording, the stimulable phosphor sheets need to be housed one by one in cassettes as described above, it is necessary to load the sheets from the stacking tray one by one into the cassettes prior to the recording of an image thereon. Therefore, it takes a long time to load each stimulable phosphor sheet into a cassette after the sheets have been prepared for image recording. Therefore it is not always possible to circulate and reuse the sheets efficiently. Also, loading of the stimulable phosphor sheet into the cassette is carried out either manually or with a special-purpose loader. The cost of the overall system increases in cases where a special-purpose loader is used, and manual loading is disadvantageous from the viewpoint of sheet processing since the sheet must be manually handled.
Accordingly, as disclosed in, for example, Japanese Unexamined Patent Publication Nos. 62(1987)-90641 and 62(1987)-164039, the applicant proposed radiation image read-out apparatuses wherein a cassette housing a stimulable phosphor sheet on which a radiation image was stored in an external image recording apparatus is fitted to a cassette holding section. The stimulable phosphor sheet is then taken out of the cassette, subjected to a read-out operation, erased, and conveyed into the employ cassette.
However, with the proposed radiation image read-out apparatuses, because the stimulable phosphor sheet is returned to the cassette after the read-out operation and erasure of the stimulable phosphor sheet are finished, the stimulable phosphor sheet must be circulated by a sheet conveyance means in the radiation image read-out apparatuses. Because the radiation image read-out apparatuses must be provided with the sheet conveyance means, the radiation image read-out apparatuses cannot be kept small in size. For example, the longitudinal and transverse lengths of the proposed radiation image read-out apparatuses are approximately equal to the total length of several stimulable phosphor sheets. Therefore, the proposed radiation image read-out apparatuses can be installed only where relatively large areas are available.